Distribution Of Processing Jobs

Some of our GIS and digital image processing tasks require several independent commands to be executed and their results combined. These commands can be easily done sequentially on a single CPU. When there are a lot of commands and/or each command is very CPU intensive, this method can be very time consuming. The user could log in to several machines and execute a few commands on each simultaneously, but this involves more bookkeeping. Also, since some machines are faster than others due to user load of CPU speed, this may be inefficient. The answer has been the development of a job distribution program that remotely executes commands on several computers simultaneously. It is simply a way of automating the process of a user logging in to several machines to execute CPU intensive operations. Virtually any non-interactive UNIX command can be executed on an available server.

The input to the program is a list of UNIX commands that can be contained in a file. When the program is executed it searches for available servers and executes one command in the list on each server simultaneously. When any server finished its command it is sent another until the list of commands has been exhausted. Using this form of job distribution, all the computers can be kept busy and results obtained in a more timely fashion.

Data Visualization

Regional biodiversity databases are complex in the number of elements to understand. The Gap Analysis of California database has many map layers, each with a large number of attributes. The vegetation database, for instance, has detailed information on dominant canopy plant species, their relative abundance, the association with other species as recurring communities, and canopy closure. Our results with the database suggest that the landscape database approach will yield useful information for regional conservation planning that goes beyond that provided by simple vegetation maps. The database contains more extensive attribute detail than these simpler land-cover type maps. Much of the information is encoded as alphanumeric codes related by lookup table to the botanical names or other more readily understandable description. For instance, to ask what is the distribution of a plant species that is dominant in the canopy in the Sierra Nevada, the user would need to know the 5-digit code number of that species and that it could occur in potentially ten different columns or items in the database. Unfortunately, this richness of the database makes it more difficult for novice users to answer their conservation or biogeographical questions. One of the project objectives was to develop new software to facilitate analysis of the species data by other botanists, ecologists and biogeographers, and the general public.

Alternative software tools were explored for developing a better interface to the GAP database to assist new users in querying the complicated spatial database. Whereas we originally expected to have to program this interface from scratch, GIS technology advanced to the point where we could adapt existing software to the task. Thus we have customized an interface (Figure 26) in ARCVIEW, a commercial desktop map analysis package, using its own programming module called AVENUE. This interface was designed to interpret the most frequently posed queries of the database while freeing the user from having to know the structure of the database or the internal coding of attributes. The interface will allow the user merely to specify a species and the interface program will interpret the request into the appropriate database query. Base maps and other biodiversity information can be added to the display with point and click techniques. Even some simple queries, analyses, and graphical summaries can be performed on-the-fly. This product will be published later this year on CD-ROM, with the software locked to the database, making it a self-executing package that will run on standard PCs.

World Wide Web

Web browsers have become the tool of choice for many users for navigating the Internet. Based on the hypertext model of traversing documents within a site and across sites, browsers are easy both for users and developers. It also has many of the built-in tools needed for our IBM project objectives to provide better access to biodiversity datasets. Therefore, we began development of a web home page in 1994 which can be accessed at http://www.biogeog.ucsb.edu/. Users can select data from our archives using two methods. The first utilizes a clickable imagemap for a region, where a user clicks on a region on a map and receives thumbnail images of the datasets available for that region along with a list of available datasets and descriptions. Each dataset can be downloaded directly with the click of a button. The second way to query the database is for the user to select both the regions and data themes of interest by clicking checkboxes which list the regions and themes (Figure 27). Once the datasets of interest have been selected and the query submitted, the user sees thumbnail images of each data theme along with a link to the real data's ftp location. The web access for the final California GAP database will be revised shortly and data will be available in several forms to assist users with different connection speeds or geographic areas of interest.